Arthrolips obscura (Sahlberg, C.R., 1833)

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POLYPHAGA Emery, 1886

CUCUJOIDEA Latreille, 1802

CORYLOPHIDAE LeConte, 1852

CORYLOPHINAE LeConte, 1852

PARMULINI Poey, 1854

Arthrolips Wollaston, 1854

This Western Palaearctic native has a wide though apparently discontinuous distribution in Europe, it is locally common in the south from France to Romania and Ukraine and is known from North Africa and many of the Mediterranean islands, it is more local and generally rare further north to Germany and Latvia Southern Sweden, and there are older records from Finland where it is now thought to be extinct. Adults have been recorded throughout the spring and summer. Typical habitats are open deciduous woodland and wooded pasture where there is plenty of decaying wood and accumulated litter, adults have been found on dry bark and exposed xylem on various broadleaf trees and among decaying wood in rot holes on willow, they also occur in large numbers among decaying litter and have been recorded under damp birch bark and among stored potatoes. They are often associated with fungoid wood and litter etc., and adults have been recorded from Fomes fomentarius (L.) Fr. 1849 and Daldinia concentrica (Bolton) Cesati & de Notaris on various trees. Both adults and larvae are thought to feed on spores and hyphae of various moulds. The species was recently added to the British list (Allen & Duff, 2013) and is so far known from several sites in South Hampshire; it was found in numbers on burnt gorse during May and September 2013 in the New Forest and, considering the very distinctive appearance of the species, was very probably a new arrival to the UK at the time. Given the general saproxylic nature of the species in Europe, and given that the species is known to disperse by flight, it is likely to be more widespread in the UK. Adults may be found by beating or sieving likely material but on the continent they have been caught in numbers in flight-interception traps and traps baited with fermenting beer (which suggests they may occur at sap runs).

Arthrolips obscurus 1

Arthrolips obscurus 1

© U.Schmidt https://www.kaefer-der-welt.de/index.htm

Arthrolips obscurus 2

Arthrolips obscurus 2

© Lech Borowiec http://www.cassidae.uni.wroc.pl/Colpolon/index.htm

Readily distinguished by its small size, 1.16-1.60 mm (although it is among the largest of the European corylophids) and general habitus. Elongate-oval and continuous in outline, with very fine overlapping  pubescence throughout and variable in colour from black to pale yellowish-brown, usually with the anterior margin of the pronotum contrastingly pale, antennae pale with the club darker, legs entirely pale. Head concealed under the pronotum, slightly elongate with large and weakly-convex eyes. Antennae 10-segmented; two basal segments long and subequal, 3 a little shorter, 4-7 small and quadrate or nearly so, and 8-10 forming a distinct club. Pronotum broadest across the base and smoothly narrowed to a rounded apical margin (from above), posterior angles perpendicular and basal margin curved, surface finely and closely punctured, evenly though rather weakly convex and without sculpture. Scutellum small but obvious, lateral margins curved and surface smooth and without microsculpture, punctured as the surrounding elytra. Elytra broadly elongate and gently curved from angled shoulders to separately-curved apical margins, finely punctured throughout, sometimes more finely so than the pronotum, and without striae. Legs short and slender, the femora hidden from above and the tibiae almost parallel-sided. Tarsi 4-segmented but appearing 3-segmented due to the diminutive third segment. Claws smooth and only slightly widened towards the base. Males may be distinguished by a U-shaped patch of pubescence on the metasternal disc.